Drill bit with staggered teeth



United States Patent Inventor App], No.

Filed Patented Assignee Allen E. Bar-dwell Princeton, New Jersey Dec. 3,1968 Dec. 8, 1970 Trident Industries Inc.

Princeton, New Jersey a corporation of Delaware, by mesne assignmentsDRILL BIT WITH STAGGERED TEETH References Cited UNITED STATES PATENTS5/1915 Buscavage 3/1917 Lane 6/1957 Stokes 8/196] Pennington I1 12/1964Cleary Primary Examiner-James A. Leppink Attorney-Kingsland, Rogers,Ezell, Eilers & Robbins 8 Claims, 5 Drawing Figs.

US. Cl 175/398, 175/412, 175/414 Int. Cl F2 lc 13/00, F2lc 13/06 Fieldof Search 175/379, 398, 399, 412, 414

ABSTRACT: A drill bit for gravity drop drills and other percussiondrills in which teeth extend outwardly from the end of i the bitdifferent distances, that is, the teeth are of or are at differentdrilling heights.

1 DRILL arr WITH STAGGERED TEETH BACKGROUND or THE INVENTION 1 Field ofThe Invention The present invention relates generally. topercussiondrilling, as in rotary air hammer drilling and in cable drop Idrilling, and more particularly to a novel drill bit incorporatingopposing teeth which are staggered vertically or are set at or i are ofdifferent drilling heights, that is, one tooth extends outwardly fromthe end of the bit further than the other.

2. Description of the Prior Art As is stated in applicant's copendingU.S'. Pat. application Ser. No. 661,560, filed Aug. 18, 1967, there'haslong existed the need fora percussion drill bit which will reducematerially the recrushing of rock material previously cut and which willmaterially increase the inches per hour drilled over standard SUMMARY orTHE INVENTION Broadly, a preferred embodiment of the present novelpercussion drill bit includes a streamlined shaft or housing sup portingtwo spaced opposed blocklike teeth at the lower end, a which may be ofthe expandable type'as illustrated in the drawings. Each tooth includesan elongated cutter insert of carbide or other suitable material. The.teethmay be of tooled steel. One tooth extends outwardly from th'e endof the bit further than the other, hence, is of greater drilling height,or has such greater effective drilling height, than the other, whichincreases the cutting effect of the bit byincreasing the unit load and,consequently, the cutting rate per hour of the drill.

This novel arrangement also substantially eliminates pinching by carbideinserts, hence, reduces breakage to a nominal percentage by drilling anoversized hole allowing the remaining or opposing carbide to be freefrom pinchingand breakage that could occur in a tight hole. Thestaggered principle causes a larger hole diameter to be drilled as thelead tooth kicksv outwardly upon impact with hole bottom.This largerdiameter hole prevents the two opposing carbides from pinching in atight hole. The high unit load created by one carbide, rather than two,results in faster drilling.

Thus, an object of the present invention is to provide a novel drill bitwhich is constructed to increase the cutting effect thereof over otherbits, hence, to increase the drilling rate per hour of the drill-ofwhich it forms apart. 1

Other objects are to provide a novel drill bit which reduces carbideinsert breakage to a nominal percentage, which is constructed to includethe principles of the present invention. The bit 10 includes a shaft 12having athreaded, reduced upper end 14 and a lower end 16 having twocavities or chambers 18 open at the ends and bottom and separated by adepending partition or wall 20.

A tooth 22 of block form including a round hole 24 with an enlargedleading portion 26 and having an insert 28 of carbide or other suitablematerial and of the configuration shown in the drawings is mounted inone cavity 18. A second tooth 30 extending a lesser distance outwardlyfrom the end of the bit,

- hence, of shorter drilling height than the tooth 22, but otherwise thesame except for a threaded hole 32 instead of the hole 24 is mounted inthe other cavity 18. Successful experimental teeth 22 have ranged fromone-eighth inch to one-half inch greater in drilling height as definedabove than associated teeth 30. With much less the carbides tend tostick and with much more the crushing effect of tooth 30diminishessharply. The teeth 22 and 30 can be of the sameheight, of course, withthe former shirnmed or otherwise positioned to extend below the latterto attain a greater effective drilling height. The teeth I 22 and 30 maybe of .solid good tool steel. The tooth 30 will crush cut rock. A heavybolt 34 with a head 36 extends through the hole 24, a hole 38 in thepartition 20, and threadedly engages the hole 32 to maintain the teeth22 and '30 in operative positions. The hole 38 is a little larger thanthe diameter of the bolt 34 to prevent undue impact on or contact withthe bolt 34 in drilling to prevent stressing or binding of the bolt 34.It is understood that variations may be made in the f teeth wear indrilling.

It will be further understood that the novel aspect of the presentimprovement of incorporating teeth of selected dif- 3 ferent drillingheights or positions extending different distances from the end of thebit may be incorporated in stationary teeth as well as adjustableteeth-Additionally, it may be included in percussion and other drillbits having more than two drill teeth, as three or four. Forgreatest'effectiveness in a highly effective, which is adapted tofunction "at its increased drilling rate for extended intervals, whichis of sturdy construction, which is adapted to multidrilling usage, andwhich otherwise fulfills the objects and advantages sought therefor.

BRIEF DESCRIPTION OF THE DRAWINGS DESCRIPTION OF PREFERRED EMBODIMENTReferring to the drawings more particularly by reference numerals, 10indicates generally a cable percussion drill bit four-tooth bit, forexample, the teeth should be in the form of an X" and not at The presentnovel drill bit is highly effective in achieving the sought objectives.Faster trouble free drilling under comparable conditions areattained'than with other bits.

It is apparent that there has been provided a drilling bit whichfulfills the objects and advantages sought therefor.

It is tobe understood that the foregoing description and theaccompanying drawing have been given by way of illustration and example.It is also to be understood that changes in form of the elements,rearrangement of parts, and substitution of equivalent elements, whichwill be obvious to those skilled in the art, are contemplated as withinthe scope of the present in vention which is limited only by the claimswhich follow.

Iclaim:

l. A percussion drill bit including a main body, at least two activedrill teeth secured in said main body, one drilling tooth extendinga-greater distance outwardly from the end of the bit than the other andbeing of greater drilling effectiveness than the other, said onedrilling tooth being the primary drilling element and effectivedeterminent of hole cross section, the other of said at least two activedrill teeth being a secondary drilling element operating within the holecross section basi- 5. The drill bit of claim 2 in which at least thetooth of eighth inch more than the other. greater effectiveness drillinghas a carbide drilling insert 8. The drill of claim 1 in which said onedrill tooth extends 6 The drill ofclaim l in which said teeth ar adjstabl outwardly from the end of the bit between substantially one- 7.The drill of claim 1 in which the said one drill tooth ex eighth andOne-half inch'more than the otherstends outwardly from the end of thebit suhstantially one-

